I had the same problem, called Apple about it. They asked “Was the hostname setup in DNS and reverse lookup setup in DNS before you first set it to Open Directory Master.” I didn’t work at my current company at the time it was first installed so I had no idea, they assumed yes. They recomended running the same scripts that afp548 did (which I had tried before and had the same issue). Their next recommendation was a full reinstall of OS X. They said if DNS isn’t completely setup before the first time you switch it to Open Directory Master something in the Kerberos scripts will fail, and appearantly never, ever work. Some people get lucky and running the Kerberos scripts by hand works, some, like me, have to start from scratch.